Jerry Cherney and Bill Cox, Soil and Crop Sciences Section, Cornell University
Research has been conducted on a range of corn silage management topics in NYS over the past few decades. This summary is based on research that has included multiple sites and/or multiple years. Issues can be divided into two basic categories: Concerns prior to planting and concerns after planting. First, we prepare for the season, and then we have a limited number of options to react to the specific weather conditions of each season.
While there are a number of options regarding plant genetics, of primary concern is the selection of the correct maturity group for your area and for the particular season (Fig. 1). You can expect to increase yield by about one ton/acre for every 10 additional maturity group days. The greater the maturity group, the higher the moisture content will be on any given fall date. Keep in mind that moisture loss per day keeps shrinking through the fall period (Fig. 2), making it increasingly difficult to reach optimum moisture in late fall.
Maturity group selection is influenced by your planting date and by your normal first frost date. 1) Plant full season hybrids from late April (if soil is dry) to late May, 2) Adjust hybrid relative maturity to planting date – mid-season hybrid from late May-~June 10, or 3) Plant early-season hybrids after June 10.
Brown-midrib (BMR) corn hybrids continue to improve in comparison to other options, and are worth considering. BMR hybrids will yield about 90% of a normal hybrid, plus or minus a few percent. On the plus side, BMR hybrids can be up to 25% higher in fiber digestibility (NDFD) than normal hybrids. Dairy feeding trials have shown that a small increase in ration fiber digestibility produces a significant increase in milk production.
While there still may be some increased potential for lodging, current BMR hybrids are much improved over the original BMR offerings. However, one issue that remains is dry down, BMR hybrids tend to retain moisture significantly longer than normal hybrids in the same maturity group. Also, there are indications that BMR types are somewhat lower in starch digestibility than floury types.
Numerous seeding rate trials over several decades in NY produced relatively consistent results (Fig. 3). Soil type has some impact on suggested seeding rates. Deep, well-drained soils => 36,000; Moist silt loam soils => 34,000, and Droughty soils => 30,000. Seeding at a rate of 35,000 is now very common in NY.
Trials comparing narrow rows (15”) with standard 30” rows have shown increased yield with narrow rows, if fertilized adequately with N (Fig. 4). Narrow rows have a more equidistant plant spacing, resulting in full sunlight being intercepted earlier in the season. The possible downside to narrow rows includes purchase of a new planter, and a row-independent harvesting head if not already on-hand. Any post-emergence applications will result in some wheel traffic damage, which can be minimized by large-width application equipment. Partial budget analysis, assuming the purchase of new equipment, shows a significant increase in returns when converting to narrow row corn.
During the Season
There is an optimum amount of N for a given field that will maximize yield, excess N application beyond the optimum amount will have negative environmental consequences. There are several alternative methods for determining side-dress N application to corn, and also methods for evaluating the relative success of the chosen application rates.
Whatever method is used to determine N application rates, it is critical to have confidence in that process, as it must adhere to federal conservation practice standards, which are mandatory for concentrated animal feeding operations (CAFOs). The process for development of Land Grant University guidelines for fertility management and for evaluating environment risk is currently being formulated.
Harvest stubble height
If excess silage yield is anticipated, corn may be harvested at a higher stubble height to increase silage quality. Yield decreases linearly and NDFD increases linearly, with increased harvest stubble height (Fig. 5). A corn plant is basically a low-quality fiber pole that holds a high-quality grain bin. Cutting the plant higher up loses some fiber (lower yield), but it concentrates the impact of the grain bin (higher quality). Conversely, cutting perennial grasses or legumes high to improve quality ends in failure, it only reduces yield.
If you are routinely cutting high to increase corn silage quality, consider switching to BMR hybrids. The typical yield loss with BMR is in the same range as the yield loss due to high stubble height. The increase in fiber digestibility with BMR, however, can be three times as great as the NDFD increase due to high stubble height.
Determining optimum moisture at harvest
Harvesting at optimum moisture content is more important than hybrid genetics selection. Optimum moisture content for making silage is between 60 and 70%, although generally the ideal moisture content is in the upper 60’s. It is nearly impossible to estimate whole plant moisture content visually. There are several methods of estimating moisture content to optimize moisture at harvest.
Growing Degree Days. On average, a 100-day hybrid will have 1200 GDD from planting to silking. Another 800 GDD is the average from silking to silage harvest. The current year’s local weather data can be used to determine the actual GDD up to the present time, and then long-term average weather data can be used to predict into the future. The shorter the prediction time period, the more accurate a GDD prediction will be.
Chop and measure moisture. A more accurate method of determining whole plant moisture is to use the harvester to chop a few hundred feet into the field and either dry a sample or use an on-board NIRS instrument to determine moisture content. While this can be very accurate, it only provides a measure of moisture for the current day. An estimate of future field drying is required (Fig. 2) to reach optimum moisture.
Cut a sample by hand. Another method is to walk through a portion of the field and cut a number of plants by hand, then chopping the plants and drying to determine moisture content. The number of plants required depends in part on the uniformity of the field. During the fall of 2019 we cut 40-50 individual plants/field out of a number of fields across central and northern NY. Since we measured individual plant moisture content, it was possible to determine the number of plants required to get a representative field moisture value. For a very uniform field, 5 plants are likely to provide a good field moisture estimate. Even with more variable fields (uneven emergence issues, etc.) 10 plants is likely to provide a reasonable estimate of field moisture.
NIRS on whole plant corn. Since estimating moisture content for harvest is critical, we are evaluating small hand-held NIR units to determine if it is possible to estimate standing whole plant corn moisture. One major issue with standing whole plants is that ear moisture changes at a very different rate than stover moisture. Ears begin drying down much earlier than the stalk, so estimates of standing plant moisture may need to include information on both ear and stover moisture status. A fast and accurate method of estimating field moisture would be very beneficial for the large acreage of corn silage in NY.
There are many important management decisions regarding corn silage that must be made prior to the start of the season. The relatively few management decisions that can be made during the growing season, particularly moisture content at harvest, can make the difference between profit and loss.